This method of flashing/flexing is pretty much not used anymore, and has been replaced by the method using RSD Lite, but hey, just in case, here ya go!
Open MultiFlashFlex and lets flash/flex! It is located in C:Program Files/Motorola/PST by default. From Motox:
In the preferences section of MFF, make sure to check the "Override existing phone software even if it is newer than the superfile software", "Master Clear phones after flexing", and "Master Reset phones after flexing" boxes. For reflashing with Reflash file and Language pack, "Master Clear..." and "Master Reset..." don't need to be checked. However, leaving them checked still won't touch the flex part of your phone either.
We will use the MonsterPack you downloaded and extracted earlier, so browse to the file and click start. When you click start, PST will say "Switching the device into flash mode,"
and Windows should display the "Found New Hardware Wizard" again, finding the "Motorola Flash Interface" and one other hardware item.
After that, wait 10-15 minutes while MFF flashes/flexes the phone.
You will then finish with the "Successful FLASH!" message! Congrats!